1. Field of the Invention
The present invention relates to an image processing device, an image processing system, and a user authentication method. The present invention more specifically relates to a technique of reducing power consumed by a human body communication terminal during user authentication performed via human body communication with a human body communication terminal held by a user.
2. Description of the Background Art
According to a technique conventionally known, a human body communication unit and a human body device make communication through the body of a person carrying the human body device, and user authentication is performed based on information the human body communication unit receives from the human body device (as described in Japanese Patent Application Laid-Open No. 2010-182203, for example). Such a technique of performing user authentication via human body communication tends to be employed in various fields in recent years, and is used for automatically unlocking a locked door of an office, for example. As an example, a mat-like antenna for human body communication with a human body communication terminal (human body device) is placed in front of a locked door of a security room, and an authentication device to automatically unlock the door is connected to the antenna. According to this authentication system, when a user stands in front of the door for entry into the security room, the human body communication terminal carried by the user and the authentication device start to make human body communication through the mat-like antenna. The authentication device performs user authentication based on information received from the human body communication terminal. If the authentication is completed successfully, the door is unlocked to allow entry into the security room.
The aforementioned authentication system makes human body communication for example as follows: the human body communication terminal applies an electric field to part of the body of a user, and the mat-like antenna detects resultant field change appearing on a surface of the body of the user. However, if the human body communication terminal keeps applying an electric field all the time to the body of the user, a battery built in the human body communication terminal drains rapidly. Hence, the aforementioned authentication system is configured such that a certain electric field is generated in the mat-like antenna, and when a user stands on the mat-like antenna, the human body communication terminal detects resultant field change to shift from a power-saving mode to a communication mode. Specifically, the human body communication terminal does not apply an electric field to the body of a user in the power-saving mode to reduce the consumption of the battery, and starts applying an electric field to the body after shifting to the communication mode. When the human body communication terminal stops detecting field change transmitted from the mat-like antenna, it shifts from the communication mode to the power-saving mode again to reduce the consumption of the battery. As a result, the human body communication terminal is in the communication mode only in a limited period such as several seconds when a user stands in front of the door of the security room, and returns to the power-saving mode after the user enters the security room. The human body communication terminal then keeps the power-saving mode, thereby allowing suppression of drain of the battery.
In terms of security, for example, an image processing device such as an MFP (multifunction peripheral) placed for example in an office authenticates a user using the image processing device, according to the situation. Thus, the user authentication technique via human body communication is also applicable for authentication of a user to use an image processing device. Specifically, the following situation may be assumed: a mat-like antenna for human body communication with a human body communication terminal is placed in front of the image processing device, and user authentication is performed by acquiring user information from the human body communication terminal carried by a user who is standing on the antenna with the intention of using the image processing device.
When using the image processing device, a user generally performs detailed setting operation relating to a job including setting for print output and setting for reading of a document, and then performs operation to instruct execution of the job. After performing the setting operation for the job and the operation to instruct execution of the job, the user may keep waiting until execution of the job is completed in the image processing device. This prolongs time when the user stands on the mat-like antenna placed in front of the image processing device, so that the human body communication terminal carried by the user keeps the communication mode for a long time. Hence, employing user authentication via human body communication as user authentication in the image processing device leads to a problem of shortened battery lifetime of the human body communication terminal.